10A or 16A MCBs?

[OneMoreFarang 53870]

Let's start with the information that I did electrical installations a long time ago in a country far away. At that time people used a few breakers for a whole house.

I also know the theory how to select wiring and a breaker for a specific load.

I know i.e. that my water heater has a rated current of 36.4A so I will use a 40A breaker for that one.

 

But how about all those "normal" power outlets and lights?

I guess for the electrical sockets I use 16A breakers.

For the LED lights 10A breakers should allow more than enough current. But does it make sense to use 10A for this and 16A for that? Or is it just easier to use 16A for everything which does not require more current like the heater, stove, etc.?

To be clear there is no misunderstanding: There will be maybe 6 separate breakers for light and 6 separate breakers for electrical sockets.

 

In theory I could change breakers later, i.e. I could install a 10A MCB and change it later to a 16A if I need it. But doing that would mean work on the breaker box which would mean switching the electricity completely off. It's obviously easier to have the MCBs ready installed, maybe with a few spares to be sure.

 

Which breakers would you use?

[Woof999 2902]

Personally I'd go with your current assumptions (10, 16 and 40 amp breakers).

 

I like 10A on the light circuits because it makes it even more obvious that those are lighting circuits.

[Crossy 46056]

10A is good on lighting with 1.0 or 1.5mm² cable (I find 1mm² is a bit small for mechanical strength).

 

Stick the outlets on a 20A if using 2.5mm² cable although only kitchen circuits are likely to get anywhere near 20A (4.4kW total) anyway.

 

Fixed appliances as appropriate for their power consumption.

[OneMoreFarang 53870]

1 hour ago, Crossy said:

only kitchen circuits are likely to get anywhere near 20A (4.4kW total) anyway.

Thanks, that's a good point. I forgot about toaster and kettle and such things.

 

 

[Crossy 46056]

6 minutes ago, OneMoreFarang said:

Thanks, that's a good point. I forgot about toaster and kettle and such things.

 

The kettle (1,800W), 4 slice toaster (1,800W) and 1,500W microwave (heating the beans for the toast) totals 23A ish, a 20A breaker would probably stay on, just long enough.

 

Two circuits in the kitchen is a good idea 🙂 

 

 

[BritManToo 76978]

11 minutes ago, Crossy said:

 

The kettle (1,800W), 4 slice toaster (1,800W) and 1,500W microwave (heating the beans for the toast) totals 23A ish, a 20A breaker would probably stay on, just long enough.

 

Two circuits in the kitchen is a good idea 🙂 

 

 

Or you could use them one at a time.

[Crossy 46056]

12 minutes ago, BritManToo said:

Or you could use them one at a time.

 

You mean rolling blackouts like Texas?

 

https://www.texastribune.org/2022/11/29/texas-power-grid-winter-ercot-forecast/

 

Madam doesn't do "one at a time", she's an all or nothing woman.

 

[sometimewoodworker 5760]

3 hours ago, Crossy said:

Stick the outlets on a 20A if using 2.5mm² cable although only kitchen circuits are likely to get anywhere near 20A (4.4kW total) anyway.

For the average house absolutely, but for my house, not so much. I have several devices that individually draw 3kW (not AC, water heater, washing machine or cooker) I will sometimes be using more than 2 at a time so I not only have 4mm² cable for those circuits but several of them.

[Crossy 46056]

6 minutes ago, sometimewoodworker said:

For the average house absolutely, but for my house, not so much. I have several devices that individually draw 3kW (not AC, water heater, washing machine or cooker) I will sometimes be using more than 2 at a time so I not only have 4mm² cable for those circuits but several of them.

 

But your place is most definitely a "special case", how many of us have overhead cranes? 

[lopburi3 13810]

When we rewired few decades ago found normal breakers seemed to be 16/32 and stuck with that (but all wires 2.5mm).  Most outlets/lights on 16 but kitchen uses several.  Reserved the 32 for water heaters.  Major cooking by gas.

[KannikaP 11720]

1 hour ago, BritManToo said:

Or you could use them one at a time.

But then you get hot beans on cold toast, not good!

[sometimewoodworker 5760]

2 hours ago, Crossy said:

 

But your place is most definitely a "special case", how many of us have overhead cranes? 

I agree, I don’t know of any private house that has one and certainly none that have an area of about 12 by 7 meters and a lift capacity of about 2.5 meters. So a "special case"? Probably, possibly unique in Thailand.

 

Though I’m sure that there are quite a few mobile cranes in private houses, for example engine cranes.

Edited December 29, 2022 by sometimewoodworker

[bluejets 701]

On 12/28/2022 at 10:55 PM, OneMoreFarang said:

Which breakers would you use?

Determining breaker size goes by cable size and length of run and earth size in MEN system.

Common outcome of any calculation usually is to use 16A rcbo's on 2.5 sq mm cable using 2.5 sq mm laid up earth and 10A rcbo's on 1.5 sq mm cabling with 1.5 sq mm laid up earth.

Multiple short runs or staring from a given point to reduce length of runs is one way to keep this impedence down below a given level.

Reason being, in the MEN system, the earth loop impedence is the governing factor in selecting the correct breaker for any given cable size.